NED Abstract

Copyright by American Astronomical Society.
Reproduced by permission
1989AJ.....97.1566K
THIN EDGE-ON GALAXIES AS A TOOL FOR THE INVESTIGATION OF LARGE-SCALE
STREAMING MOTIONS IN THE UNIVERSE
IGOR KARACHENTSEV
Special Astrophysical Observatory, USSR Academy of Sciences,
St. Zelenchukskaya, Stavropolskij Kraj 857140, USSR
and
Arecibo Observatory, National Astronomy and Ionosphere Center, Box 995,
Arecibo, Puerto Rico 00613
Received 7 November 1988; revised 23 January 1989
ABSTRACT
When the Tully-Fisher relation is used to determine the distances to
galaxies, edge-on spiral galaxies are usually excluded, because of the
large fluctuations introduced by the internal extinction in these objects.
Based on a sample of 324 galaxies observed at Arecibo, we demonstrate that
this effect is less significant than has been usually assumed. Moreover, we
show that the scatter of galaxies in the TF diagram ("H I profile
width-linear diameter") steadily decreases, when the axial ratio a/b
increases. For the flattest and the most inclined galaxies (a/b > 7), the
scatter in the TF diagram yields a root-mean-square error in distance
estimates of 10^+/- 0-09^. Not only the H I linewidths but also the H I
fluxes of flat galaxies are strongly correlated with their optical
diameters: at a given flux, the rms scatter in diameter is only 10^+/-
0.03^. At present, the effect of "latent parameters" on the TF diagram
cannot be properly estimated, due to the lack of reliable photometric data
for a representative sample of flat galaxies. Using the photometric data of
Watanabe (1983), we have obtained the rms deviation of 10 +/- ^0.048^ with
respect to the relation W_H I_ proportional to h^0.5^ I^0.5^), which
surprisingly resembles a similar relation, {sigma}_{nu}_, proportional to
R^0.72^_e_ I^0.65^_e_, that has been derived for E galaxies (Hoessel et al.
1987). We have applied the criterion a/b > 7 to select 1547 flat galaxies
from the UGC, ESO(B), and MCG catalogs. Their distribution over the sky has
essentially less contrast than in the case of other galaxies and, in
particular, it does not show a signature of the Local Supercluster. Here,
we give a brief description of the new Catalogue or Flat Galaxies (FGC),
currently in preparation, which will cover the whole sky with an effective
depth z_e_~0.05 and will contain about 8000 objects. The catalog has
several characteristics that make it particularly suitable for the studies
of large-scale streaming motions in the universe: (i) the catalog members
are disklike, flat galaxies with a simple structure; (ii) the selection
criterion used (a/b > 7) makes the sample morphologically homogeneous;
(iii) the 21 cm line detection rate of these galaxies is nearly 100%; and
(iv) the flat galaxies avoid volumes occupied by groups and clusters so
that their structure remains undisturbed and they are not affected by large
virial motions.